PTAT current generators may be used in particular but not exclusively in temperature sensors or else to generate a bandgap voltage reference.
A conventional solution for producing a device for generating a reference current proportional to absolute temperature (PTAT current) envisages the use of means connected to the terminals of a core, comprising for example a resistor and two bipolar transistors of different sizes mounted as diodes (or else in the two branches of the core two different numbers of bipolar transistors of the same size mounted as diodes), these means being designed to equalize the voltages across the terminals of the core, the latter then being traversed by an internal current proportional to absolute temperature.
An output module delivers to an output terminal the PTAT reference current on the basis of the internal current.
An important parameter of a PTAT current generator is the power supply voltage rejection rate, known by the person skilled in the art by the acronym PSRR (“Power Supply Rejection Ratio”).
More precisely, when the power supply voltage of the generator varies, it results in a variation in the PTAT current delivered as output. The PSRR parameter is the ratio of the variation of the power supply voltage to the corresponding variation of the PTAT output current.
In prior art devices, obtaining good power supply voltage rejection, that is to say a high PSRR parameter, requires using a high power supply voltage.